selftests/powerpc: Add automatically allocating read_file

A couple of tests roll their own auto-allocating file read logic.

Add a generic implementation and convert them to use it.
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230203003947.38033-6-bgray@linux.ibm.com

tools/testing/selftests/powerpc/include/utils.h

@@ -42,6 +42,7 @@ int parse_ulong(const char *buffer, size_t count, unsigned long *result, int bas
 
 int read_file(const char *path, char *buf, size_t count, size_t *len);
 int write_file(const char *path, const char *buf, size_t count);
+int read_file_alloc(const char *path, char **buf, size_t *len);
 int read_long(const char *path, long *result, int base);
 int write_long(const char *path, long result, int base);
 int read_ulong(const char *path, unsigned long *result, int base);

tools/testing/selftests/powerpc/nx-gzip/gzfht_test.c

@@ -143,42 +143,6 @@ int gzip_header_blank(char *buf)
 	return i;
 }
 
-/* Caller must free the allocated buffer return nonzero on error. */
-int read_alloc_input_file(char *fname, char **buf, size_t *bufsize)
-{
-	int err;
-	struct stat statbuf;
-	char *p;
-	size_t num_bytes;
-
-	if (stat(fname, &statbuf)) {
-		perror(fname);
-		return -1;
-	}
-
-	assert(NULL != (p = (char *) malloc(statbuf.st_size)));
-
-	err = read_file(fname, p, statbuf.st_size, &num_bytes);
-	if (err) {
-		perror(fname);
-		goto fail;
-	}
-
-	if (num_bytes != statbuf.st_size) {
-		fprintf(stderr, "Actual bytes != expected bytes\n");
-		err = -1;
-		goto fail;
-	}
-
-	*buf = p;
-	*bufsize = num_bytes;
-	return 0;
-
-fail:
-	free(p);
-	return err;
-}
-
 /*
  * Z_SYNC_FLUSH as described in zlib.h.
  * Returns number of appended bytes
@@ -245,7 +209,7 @@ int compress_file(int argc, char **argv, void *handle)
 		fprintf(stderr, "usage: %s <fname>\n", argv[0]);
 		exit(-1);
 	}
-	if (read_alloc_input_file(argv[1], &inbuf, &inlen))
+	if (read_file_alloc(argv[1], &inbuf, &inlen))
 		exit(-1);
 	fprintf(stderr, "file %s read, %ld bytes\n", argv[1], inlen);
 

tools/testing/selftests/powerpc/syscalls/Makefile

@@ -6,4 +6,4 @@ CFLAGS += -I../../../../../usr/include
 top_srcdir = ../../../../..
 include ../../lib.mk
 
-$(TEST_GEN_PROGS): ../harness.c
+$(TEST_GEN_PROGS): ../harness.c ../utils.c

tools/testing/selftests/powerpc/syscalls/rtas_filter.c

@@ -8,6 +8,7 @@
 #include <byteswap.h>
 #include <stdint.h>
 #include <inttypes.h>
+#include <linux/limits.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/syscall.h>
@@ -50,70 +51,16 @@ struct region {
 	struct region *next;
 };
 
-int read_entire_file(int fd, char **buf, size_t *len)
-{
-	size_t buf_size = 0;
-	size_t off = 0;
-	int rc;
-
-	*buf = NULL;
-	do {
-		buf_size += BLOCK_SIZE;
-		if (*buf == NULL)
-			*buf = malloc(buf_size);
-		else
-			*buf = realloc(*buf, buf_size);
-
-		if (*buf == NULL)
-			return -ENOMEM;
-
-		rc = read(fd, *buf + off, BLOCK_SIZE);
-		if (rc < 0)
-			return -EIO;
-
-		off += rc;
-	} while (rc == BLOCK_SIZE);
-
-	if (len)
-		*len = off;
-
-	return 0;
-}
-
-static int open_prop_file(const char *prop_path, const char *prop_name, int *fd)
-{
-	char *path;
-	int len;
-
-	/* allocate enough for two string, a slash and trailing NULL */
-	len = strlen(prop_path) + strlen(prop_name) + 1 + 1;
-	path = malloc(len);
-	if (path == NULL)
-		return -ENOMEM;
-
-	snprintf(path, len, "%s/%s", prop_path, prop_name);
-
-	*fd = open(path, O_RDONLY);
-	free(path);
-	if (*fd < 0)
-		return -errno;
-
-	return 0;
-}
-
 static int get_property(const char *prop_path, const char *prop_name,
 			char **prop_val, size_t *prop_len)
 {
-	int rc, fd;
-
-	rc = open_prop_file(prop_path, prop_name, &fd);
-	if (rc)
-		return rc;
+	char path[PATH_MAX];
 
-	rc = read_entire_file(fd, prop_val, prop_len);
-	close(fd);
+	int len = snprintf(path, sizeof(path), "%s/%s", prop_path, prop_name);
+	if (len < 0 || len >= sizeof(path))
+		return -ENOMEM;
 
-	return rc;
+	return read_file_alloc(path, prop_val, prop_len);
 }
 
 int rtas_token(const char *call_name)
@@ -138,22 +85,14 @@ int rtas_token(const char *call_name)
 static int read_kregion_bounds(struct region *kregion)
 {
 	char *buf;
-	int fd;
-	int rc;
+	int err;
 
-	fd = open("/proc/ppc64/rtas/rmo_buffer", O_RDONLY);
-	if (fd < 0) {
-		printf("Could not open rmo_buffer file\n");
+	err = read_file_alloc("/proc/ppc64/rtas/rmo_buffer", &buf, NULL);
+	if (err) {
+		perror("Could not open rmo_buffer file");
 		return RTAS_IO_ASSERT;
 	}
 
-	rc = read_entire_file(fd, &buf, NULL);
-	close(fd);
-	if (rc) {
-		free(buf);
-		return rc;
-	}
-
 	sscanf(buf, "%" SCNx64 " %x", &kregion->addr, &kregion->size);
 	free(buf);
 

tools/testing/selftests/powerpc/utils.c

@@ -65,6 +65,64 @@ int read_file(const char *path, char *buf, size_t count, size_t *len)
 	return err;
 }
 
+int read_file_alloc(const char *path, char **buf, size_t *len)
+{
+	size_t read_offset = 0;
+	size_t buffer_len = 0;
+	char *buffer = NULL;
+	int err;
+	int fd;
+
+	fd = open(path, O_RDONLY);
+	if (fd < 0)
+		return -errno;
+
+	/*
+	 * We don't use stat & preallocate st_size because some non-files
+	 * report 0 file size. Instead just dynamically grow the buffer
+	 * as needed.
+	 */
+	while (1) {
+		ssize_t rc;
+
+		if (read_offset >= buffer_len / 2) {
+			char *next_buffer;
+
+			buffer_len = buffer_len ? buffer_len * 2 : 4096;
+			next_buffer = realloc(buffer, buffer_len);
+			if (!next_buffer) {
+				err = -errno;
+				goto out;
+			}
+			buffer = next_buffer;
+		}
+
+		rc = read(fd, buffer + read_offset, buffer_len - read_offset);
+		if (rc < 0) {
+			err = -errno;
+			goto out;
+		}
+
+		if (rc == 0)
+			break;
+
+		read_offset += rc;
+	}
+
+	*buf = buffer;
+	if (len)
+		*len = read_offset;
+
+	err = 0;
+
+out:
+	close(fd);
+	if (err)
+		free(buffer);
+	errno = -err;
+	return err;
+}
+
 int write_file(const char *path, const char *buf, size_t count)
 {
 	int fd;